I have a 94 chevy truck and the rear tail light don't work. Running light and turn signal work. Changed out the switch on the brake pedal and the muti function wire on the column. Still no lights what else do i need to do to get them to work without having to take it to a shop.

Check the brake light switch on the brake pedal. Sounds like it slipped out of adjustment. When pedal is depressed, the button on switch will extend and be on to pass current to the bulbs.
Also, you need to figure out the tail lights: those two filament bulbs are for park lights and for brakes/turn signals. One filament is for the parks, the other filament is for both brake and turn signals. American cars have the brake lights wired through the turn signal switch- from the brake light switch on the brake pedal to the turn switch, and then out to the rear bulbs for brakes and, or turn signals.

feed supply problem somewhere ?but where ? try checking the wiring loom at the rear or as its called in american "pigs tails"

This will either be a fuse or the brake light switch which is on the pedal it's self. More likely the switch as these are fickle at best.

check for power at the wires going intop the tail lights, real common that the circuit board is bad, but unlikely both at the same time. The tag, tail lights and brakes are 2 different systems. Do the turn signals work normally? if so the wiring from the turn signal switch to the brake lights is GOOD. the stop light switch had\s a ORANGE wire that should have 12V if not ck STOP LPS fuse, when brake pedal is depressed, the WHITE wire is 12V (at the stop light switch) if that is OK, the turn signal switch COULD be bad. The wiring harness plug is near the back left under the tailgate, see if that is disconnected?

It could be a bad multifunction (turn signal) switch. The way that switch works, it is possible that it can turn on the front blinker and not the rear one. It also cancels the brake circuit so the turn signal can work with the brake pedal depressed.

However, a more likely cause would be a break in the YELLOW/BROWN wire at the rear of the truck. It is common for the connector to get corroded at the left rear frame area where the bed harness connects to the vehicle harness. If you have trailer connections spliced into the wiring harness, these connections are also prime candidates for corrosion. I would look there first. Inspect these harnesses thoroughly all the way up and into the tail light assembly.

If the wires under the back of the truck look good, then I would check for power coming out of the turn signal switch. The wire at the turn signal switch is plain YELLOW (with no brown tracer). It is Pin (M) on the turn signal switch connector. The front signal is a LIGHT BLUE wire at the turn signal switch Pin (H). If you probe these with a test lamp, they should both work the same except the yellow wire will be hot with the brake pedal depressed and the switch NOT in the left turn position. If there is no power at the switch connector, replace the switch.

Sounds like a blown fuse or a ground wire broke.

check the relays and connections at the tail lights and under the truck, has the truck ever been off road or in deep water?

could be brake light switch but i would be more inclined to think the signal switch is bad, the brake light circuit goes from the pedal to to the turn signal switch then to the taillights

test and replace the brake light switch, it is located at the top of the arm the brake pedal is attached to.

Brake light switch, located on upper brake pedal should be checked, that is most likely your brake light issue, but U say tail lights aren't working, but running lights do, tail lights and running lights I would consider to be the same, so can u clarify that for me? Let me know how the u do w/ brake light switch, and if u have issue w/ tail lights?